1. Field of the Invention
The present invention relates to a pump dispenser for sucking and discharging liquid by virtue of reciprocal movement of a plunger.
2. Description of Related Art
Conventionally, a liquid dispenser (liquid discharging device) mainly has an arrangement where liquid packed in a syringe is pressurized for a short time and pushed by air or a valve is opened for a short time after pressurizing the liquid.
However, since discharge accuracy is not so high and minute discharge control is difficult according to such arrangement, a pump dispenser has come to be used in response to such demand.
An easily-controllable pump dispenser such as gear pump in proportion to rotation, a viscosity pump, a screw pump and a positive-load pump using an automatic valve is used as the above pump dispenser. Though the dispensers have higher accuracy than dispensers other than pump-type, further improvement in accuracy and minute discharge required for very small amount discharge dispenser used for medicine analyzer etc. and a dispenser for discharging adhesive for bonding IC chips in semiconductor manufacture line has been difficult.
A forced valve plunger pump dispenser capable of achieving high accuracy, though control thereof becomes slightly difficult, has been used for the area requiring high accuracy and minute discharge control. The following dispensers are such dispensers.
(1) D-Cut Plunger Pump
This pump is a combination of a plunger barrel with a distal end thereof being shut and having suction and discharge ports on both sides thereof and a D-cut plunger pump for rotatably switching a valve, which is simple and excellent except for disadvantages where minute leakage and inevitable residence portion are generated and very small amount of discharge in the range from micro to nano-liters is difficult.
(2) Rotary Valve Plunger Pump
This pump is a combination of independently provided planar valve, cylindrical valve and plunger. Since the valve and the plunger are independently provided, residence portion is increased.
(3) Cylindrical Plunger Pump
As shown in Japanese Patent Laid-Open Publication No. Hei 2-55878 and Japanese Patent Laid-Open Publication No. Hei 2-230975 filed by the Applicant of the present application, this pump has an integrated concentric disposition of a planar valve, a cylindrical valve and a plunger, whereby the residence portion is extremely reduced and accuracy is substantially improved as compared to the above (1) and (2) pumps. However, since sealing structure becomes so complicated that it is difficult to avoid in-liquid pump structure.
(4) Planar Valve Plunger Pump
Though the discharge accuracy can be greatly improved in the above (3) arrangement, sealing structure becomes complicated. Accordingly, the Applicant of the present application has developed a planar valve plunger pump dispenser as shown in Japanese Patent Laid-Open Publication No. Hei 9-324743, where the two planar valves and a plunger are integrated to greatly reduce the residence portion to improve accuracy and simplify a sealing structure thereof.
However, according to the planar valve plunger pump dispenser disclosed in Japanese Patent Laid-Open Publication No. Hei 9-324743, velocity (time per one discharge) is difficult to be increased and durability thereof is inferior.
Specifically, the dispenser has a clutch to rotate and stop a pump block to which the plunger is inserted so that the block stops at a position where the hole for the plunger to be inserted corresponds to a suction hole and a discharge hole during suction movement and discharge movement. Accordingly, two rotations and stop movements are required per one cycle of discharge movement, thereby limiting reduction of operation time per one cycle.
Further, in the above dispenser, since a ball screw is used to advance and retract the plunger relative to the pump block, the operation time is difficult to be reduced and, when the operation time is reduced, durability thereof is deteriorated. Specifically, though the ball screw has to be advanced and retracted at a high speed in order to reduce discharge time, it is difficult for a ball screw to conduct such short-distance reciprocal movement at a high speed, and there can be great abrasion, thereby deteriorating durability.
An object of the present invention is to provide a pump dispenser capable of improving accuracy with less fluctuation of discharge per one time, having excellent durability and capable of high-speed movement.
A pump dispenser according to the present invention includes: a valve block having a first slide contact surface; a pump block having a second slide contact surface adapted to be in contact with the first slide contact surface of the valve block; a plunger inserted to a single plunger insert hole drilled along an axial direction of the pump block, the plunger being slidable in the axial direction; a pump-driving shaft supported by the pump block, the pump-driving shaft being rotatable with the pump block and advanceable toward and retractable from the pump block together with the plunger; a rotary driver for controllably rotating the pump-driving shaft per one rotation unit; and an advancement and retraction driver for advancing and retracting the pump-driving shaft relative to the valve block, in which the valve block has a discharge port for intercommunicating a discharge opening formed on the first slide contact surface with a discharge hole formed on an outside opposite to the first slide contact surface and a suction port for intercommunicating a suction opening formed on the first slide contact surface with a supply hole facing a liquid supply side, in which the plunger insert hole of the pump block is drilled at a position capable of being in communication with the discharge opening and the suction opening of the valve block along an axial direction, and in which the advancement and retraction driver includes a follower attached to the pump-driving shaft and a guide member capable of adjusting inclination angle thereof relative to a reference surface orthogonal with the axial direction of the pump-driving shaft, the guide member guiding the follower moving in accordance with the rotation of the pump-driving shaft to advance and retract the pump-driving shaft.
According to the present invention, since a cam mechanism including the guide member and the follower is used in rotating, advancing and retracting the pump-driving shaft without using a ball screw, high-speed rotation, i.e. high-speed discharge is possible while improving durability.
Further, since only a single plunger insert hole and plunger are provided, the discharge motion is conducted by rotating the pump-driving shaft, i.e. the pump block, for one time, so that the discharge motion of each time can be made identical, thereby improving accuracy of discharge amount of each time.
Further, since the discharge amount can be adjusted by adjusting the inclination angle of the guide member in proportion to the inclination angle, the discharge amount can be more easily adjusted and changed as compared to the arrangement using a cam mechanism, thereby enhancing usability of the dispenser.
An end of the guide member may preferably be supported by a fixed shaft fixed to a case in a pivotable manner, and the pump dispenser may preferably further includes a discharge controller capable of adjusting the inclination angle relative to the reference surface of the guide member by moving the other end of the guide member in the axial direction of the pump-driving shaft.
According to the above arrangement, since the inclination angle of the guide member can be adjusted only by moving the other end of the guide member in the axial direction of the pump-driving shaft by the discharge controller, the discharge amount can be easily adjusted.
The discharge controller may preferably be capable of moving the other end of the guide member from a position on a reference surface at the same level as the fixed shaft to move away from the pump block relative to the fixed shaft.
According to the above arrangement, the condition when follower shaft is close to the fixed shaft, i.e. when the pump-driving shaft (and the plunger) is the most adjacent to the valve block, can be fixed. Accordingly, by setting the plunger tip to be at the level of the end surface of the plunger insert hole of the pump block at the above position, the dead space when the plunger goes the closest toward the valve block can be reduced, thereby preventing residence of the liquid in the plunger insert hole. Further, the adjustment range of the stroke when the guide member is inclined can become the widest, so that the adjustment range of the discharge amount can be enlarged.
The discharge controller may preferably include a micrometer and the other end of the guide member may preferably be moved interlocking with the advancement and retraction of a spindle of the micrometer.
With the micrometer, the discharge amount can be set using the scale of the micrometer, and the setting work can be easily conducted with high accuracy.